NOTE DIFFICULTY IN REACHING OBJECTS AND BODY PARTS: A SENSORYMOTOR DISCONNEXION SYNDROME ' Gianfranco Denes, Franco Caviezel and Carlo Semenza (Clinica Neurologica dell'Universita di Padova) INTRODUCfION Difficulty in reaching targets outside the body under visual control, in the absence of elementary neurological deficits, has been described since Crouigneau's (1884) original observations and termed "troubles du sens de l'espace" (Badal, 1888), "optische Ataxie" (Balint, 1909), and "disturbance of visual orientation" (Holmes, 1918b). This difficulty, also called 'visuomotor ataxia' (Rondot, De Recondo and Ribadeau-Dumas, 1977) may affect one or both hands, and may be present in one (Riddoch, 1935) or both visual fields. In most cases the lesions have involved the occipito-parietal regions bilaterally (Ratcliff and Davies-lones, 1972; Damasio and Benton, 1979). According to Balint (1909) the disorder was due to the lack of control of sight on movement, while Smith and Holmes (1916), Holmes (1918a, 1918b) and Holmes and Horrax (1919) attributed the defect to the lack of integration of the information coming from the retinae and proprioceptive impressions coming from the extraocu" lar and neck muscles and from the labyrinths. The patients they described as unable to reach objects in the space were also unable to judge which was the nearer of two objects, to determine. the relative length of two lines or the relative size of two objects, bumped into obstacles when walking, experienced difficulty in recognizing movements in the sagittal plane, and had various disorders of ocular movements and visual attention; furthermore some cases had a loss of stereoscopic vision. In recent years Haaxma and Kuypers (1974) showed that a disconnection of the motor area from the striate area could produce in animals "a defect in visual guidance of controlateral hand and finger movements". Boller, Cole, Kim, Mack and Patawaran (1975) and Rondot, De Recondo and Ribadeau-Dumas (1977) have offered a similar interpretation for their cases of visuo-motor ataxia. Such cases, however, showed in the great majority normal ability to point to their own body parts. On the other hand there exist subjects who, following cortical damage and in the absence of obvious comprehension disturbances, show a selective deficit in pointing to their body parts on verbal command coupled with normal ability to reach targets outside their body (autotopoagnosia). Unfortunately, the physiological mechanism responsible for the latter symptom is ill-defined since the majority of authors discussed the disorder on the level of theoretical speculations. Pick (1908) postulated a body schema disturbance to be I This work was partially supported by a grant of the Ministero della Pubblica Istruzione to the senior author. Cortex (1982) 18,165-173.